The Na+/I- symporter mediates active iodide uptake in the intestine

Juan Pablo Nicola, Cécile Basquin, Carla Portulano, Andrea Reyna-Neyra, Monika Paroder, Nancy Carrasco

Research output: Contribution to journalArticle

91 Scopus citations

Abstract

Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I-) utilization. From the bloodstream, I - is actively taken up via the Na+/I- symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I- to the newborn in the milk. The molecular basis for intestinal I- absorption is unknown. We sought to determine whether I- is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I - itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I- in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I - uptake in these cells was also kinetically similar to that in thyrocytes. I- downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I- accumulation. Therefore, NIS is a significant and possibly central component of the I- absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.

Original languageEnglish (US)
Pages (from-to)C654-C662
JournalAmerican Journal of Physiology - Cell Physiology
Volume296
Issue number4
DOIs
StatePublished - Apr 1 2009

Keywords

  • Active iodide transport
  • Dietary iodide absorption
  • Enterocyte brush border
  • Sodium/iodide symporter

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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